Control over Light Soaking Effect in All‐Inorganic Perovskite Solar Cells

Abstract Light soaking (LS) has been reported to positively influence the device performance of perovskite solar cells (PSCs), which, however, could be potentially harmful to the loaded devices due to the unstable output. There are very few reports on controls over the LS effect, especially in all‐inorganic PSCs. In this study, a remarkable LS induced performance enhancement of CsPb(I 1− x Br x ) 3 based PSCs is presented. In situ grazing‐incidence wide‐angle X‐ray scattering measurements quantize the temperature increase under illumination and reveal a radiative heating‐induced lattice expansion. The device curing time is shortened with the increased Br/I ratio, evidently correlated with their distinct mobility and activation energy. It is suggested that LS could promote the migration of halide ions, giving rise to notable defect passivation and thus device improvements. Based on these understandings, an effective means is proposed to suppress the LS effect, which is to incorporate slightly over‐stochiometric PbI 2 in precursor, and a champion PCE of 18.14% in all‐inorganic PSCs with significantly reduced device curing time is obtained.